Clothes made from cellulose fabrics often develop a grayish cast or appearance with wear and repeated washing. This unwanted effect is particularly evident in garments dyed with dark colors. It is believed that the grayish cast is caused, at least in part by generation of disordered fibers through mechanical action. The mechanical action incident to washing tears, splits, and/or breaks fibers, generating superficial disorder at the surface of the strands or threads from which the garment is made. Even after a thorough washing in which all ordinary dirt, e.g., protein, oil, starch and dust, has been removed, the clothes look faded and worn.
U.S. Pat. No. 4,738,682 disclosed a color clarification method involving the use of cellulase alone as a color clarification agent. As defined herein, a "color clarification agent" is an agent involved in the preservation or restoration of the initial appearance of a colored fabric throughout multiple washing cycles by removing fuzz and pills from the surface of the garment and/or fabric. Such an agent has, to some extent, improved the appearance of washed fabrics relative to washed fabrics not treated with the agent. Colored fabrics dyed with fugitive dyestuffs, such as those belonging to the direct dye class of dyes, develop a particularly faded appearance after repeated washing due to loss of dye from the fabric. The loss of color contributes to the aged look of the fabric. This color loss is not maintained or restored by treatment with cellulase alone. Therefore, a need exists for an improved agent which will more effectively restore the attractive look of fabrics which have developed a grayish cast after frequent washing, or maintain the original appearance of fabrics that are washed many times, thereby offering the consumer a chance to avoid discarding worn looking, but still serviceable cellulose fabric garments.
Some surfactants have been found to boost the action of cellulase. These include ethoxylated C.sub.12 -C.sub.20 alcohols or alkyl-phenols with 10-100 ethoxy groups (WO 91/19794). Polymers of one or more monomers selected from the group of vinyl pyrrolidone, vinyl alcohol, vinyl carboxylate (especially polyvinyl acetate), acrylamide, soluble acrylates, and copolymers of these (WO 91/19807) are reported to increase cellulase enzymatic effect for color clarification of textiles. However, no other polymers are known in the art to have such boosting action.
Polymers, such as polyvinyl pyrrolidone, are known in the art to suspend particles in solution and sequester dyes in solution, thereby preventing dye transfer from one fabric to another (V. B. Croud, The influence of washing powder components on dye loss and dye fading, JSDC, 112 (1996) 117-122; F. Runge et al., Binding equilibria of multiazo dyes with polymeric dye transfer inhibitors, Berichte der Bunsen-Gesellschaft-Physical Chemistry Chemical Physics, 100, No. 5 (1996) 661-670). Other polymers reported to provide dye transfer inhibition are polyamine N-oxides (WO 95/33028) and combinations of polyamino acids and polyalkylene glycols (WO 95/16767) but these have not been reported to give improvement of cellulase color clarification performance.